Fixing device of the inner end of a regulating hairspring in a timepiece



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A fro/HIE Ys 3,274,766 FIXING DEVICE OF THE INNER END OF A REGU- LATING HAIRSPRING IN A TIMEPIECE Jean-Jacques Desaules and Henri-Louis Henchoz, Le Locle, Switzerland, assignors to Fabrique dHorlogerie Chs. Tissot et Fils S.A., Le Locle, Neuenburg, Switzerland Filed Nov. 16, 1964, Ser. No. 411,286 Claims priority, application Switzerland, Jan. 31, 1964, 1,156/64 8 Claims. (Cl. 58-115) This invention relates to a fixing device of the inner and of a regulating hair-spring of a timepiece, comprising a collet having a curved side surface against which at least a part of the inner coil of the hair-spring is held applied.

It also relates to a manufacturing method of this de vice and to a molding member for performing the method.

It has already been proposed to secure the inner end of an horological hair-spring on the collet by gluing. In this way the side surface of the collet can be given a curvature equal to that of the inner coil of the hairspring and this coil can be fixed without deforming the same. An eccentric development of the hair-spring on oscillating can be avoided in that way and the active portion of the hair-spring can extend inwards to the immediate vicinity of the oscillating axis of the balancewheel.

However, the effective manufacture of such fixing devices encountered till how such difficulties that it could not be undertaken. When glue is applied on a part of the side surface of the collet and when the hair-spring is then applied on the surface supplied with glue, the glue amount comprised between these two pieces cannot be metered exactly. Surface tension and viscosity have often unexpected effects. The hair-spring can move aside or become distorted upon drying. However, it is necessary to introduce, between the hair-spring and the collet an amount of glue sufficient in order to provide a fixation which will support the alternating stresses at high fre quency that are transmitted from one piece to the other.

It is an object of the invention to propose a fixing device as well as a manufacturing method of this device and a means for performing this method which enable to solve all these problems easily.

Therefore, the device is characterized in that the collet is provided with a lodging which is open in the said side surface and in that the hair-spring is secured to the collet by means of a solidified mass of glue filling said lodging up to a level higher than the upper level of the hairspring, and adhering to its walls as well as to the hairspring; the method is characterized in that a molding member made out of a material at which the glue used does not adhere is juxtaposed to the collet so as to close said lodging tightly, and in that glue is introduced through a part of this lodging which remains open. The molding member for performing this method is characterized in that it consists of a plastic material to which the glue used does not adhere, and in that it comprises an upper planar surface capable to support a part of the neighbouring hair-spring coils, a projection extending above said upper surface and being arranged so that it can be inserted between the last and the first but last coil, and an inner curved side surface matching the collet side surface in which opens a cavity opened upwards.

The accompanying drawing represents, by way of example, one embodiment of the device according to the invention and it illustrates one example of performing the method.

FIGURE 1 is a plan view of said embodiment, and

United States Patent 3,274,766 Patented Sept. 27, 1966 ice FIGURE 2 is a part axial section thereof.

FIGURE 1 represents a collet I mounted on a cylindrical rod 2 protruding from a receptacle 3 on the upper surface of which the collet 1 lies. A hair-spring 4 is set in place around collet 1, its different coils being supported in part by the receptacle 3 and in part by a molding member 5 made of a plastic material and having generally a cylindrical shape with a planar upper surface 6. This member bears against collet 1. It enables exactly metering a mass of glue 7 introduced in part into a lodging 8 of the collet. The hair-spring 4 is embedded in this glue mass and thus secured to the collet.

As shown in FIGURE 1, the collet 1 has in a plan view the general shape of a rhornbus with two apices cut away. Its side surfaces comprise two diametrically opposed curved surfaces 9 and 10, having a cylindrical shape. The end portion of the inner coil of the hairspring 4 is frictionally inserted in a groove 11 of rectangular cross-section provided horizontally in the side surface 9. In a similar groove 12 provided in the side surface 10 extends a part of the hair-spring 4 which is situated approximately in the middle of the inner coil. It will be observed that the inner hair-spring coil extends between grooves 11 and 12 substantially along a path corresponding to its natural curvature and wholly situated outside the collet.

The lodging 8.is obtained by providing a blind cylindrical hole having an axis parallel to that of the collet, in the outer portion delimited by surface 10. This hole is positioned so that its wall intersects surface 10 over a width substantially smaller than the hole diameter in order to form edges gripping the solidified glue mass 7 thus adding a supplemental mechanical resistance to the adhesion force.

The molding member 5 comprises a projection 13 extending above surface 6 in the vicinity of its periphery and a concave lateral cut-out, which extends up to the vertex of projection 13 and the bottom of which has the shape of the side surface 10 of collet 1. The projection 13 is finally provided with a lateral cavity 14 which extends exactly opposite lodging 8 when the molding member 5 is in place as shown in the drawing. Member 5 is then applied against the side surface 10 of the collet so that no joint subsists between these two pieces. The projection 13 and the collet 1 constitute a mold closed on all sides, except upwards, and consisting of cavity 14 and lodging 8. The hair-spring 4 extends across this mold approximately in the middle of its height while leaving all the sides thereof.

The glue mass 7 is introduced into the mold from upside and it will be observed that this mass wholly surrounds the part of hair-spring 4 which extends across the mold.

To make the molding member 5, the thermoplastic material known as Delrin (registered trademark) is preferably used and as glue, a usual glue such as Araldite (registered trademark) which can dry as a compact and solid mass, firmly adhering to metallic surfaces such as those of the hair-spring 4 and the collet 1.

It is known that thermoplastic materials of the type Delrin have the property that they cannot be glued by means of such glues so that, after solidification of mass 7, it is possible to remove the molding member 5 without exerting any effort on the collet and without executing cutting operations. The molding member 5, once re moved, is perfectly clean and can immediately be used again for a new operation.

Moreover, the solidified glue mass 7 wholly surrounds the part of hair-spring 4 Which extends across the lodging 8. It extends beyond the boundaries of this lodging and covers at least a part of the side surface 10 of the collet, but in radial direction, it does not extend beyond the pre- 6 determined value depending on the depth of cavity 14, i.e. this radial extension is very exactly limited to the desired value. The depth of cavity 14 can thus be chosen in such a way that the glue mass 7 will never come in contact with the second coil of the hair-spring during a complete oscillation.

The assembling operations of collet 1 to hair-spring 4 accordingly consist in cutting the hair-spring to the desired diameter, then in inserting the end and the middle part of the last coil into the grooves 11 and 12, which ensures the whole hair-spring to be centered and held flat.

Once the collet has been set on the receptacle (2, 3), the

molding member 5 is set in place by inserting the projection 13 between the second and the first coil so as to apply the latter against the bottom of groove 11. Member 5 is then in contact with the side surface 10. The outer coils of the hair-spring are supported by member 5 and receptacle 3. The hair-spring is centered and held flat by the collet groove. Then it sufiices tofill the cavity 14 and the lodging 8 with glue. Once the latter is solidi- -in combination, an outer convex side surface portion on the collet, a portion of the hair-spring inner coil having an inner side surface applied against said outer convex side surface portion of the collet, a blob of material firmly fixed to said portion of the hair-spring inner coil and having a projection extending inwards from the inner side surface thereof, and a lodging in the collet provided in said outer convex said surface portion thereof, the inwardly extending projection of said blob of material entering said lodging and constituting therewith a fixing connection ensuring the anchorage of the hair-spring to the collet.

2. In the combination of claim 1 said projection of said blob being adhesively fixed wihin said collet lodging.

3. In the combination of claim 1, said blob consisting of adhesive material and said projection of said blob filling up said collet lodging.

4. In the combination of claim 3, said collet lodging extending, in height, up to the collet upper surface.

5. In the combination of claim '3, the collet having a side surface being provided with a groove the bottom of which constitutes said outer convex said surface portion, said groove having a rectangular cross-section in which the hair-spring blade is inserted.

6. In the combination of claim 5, said lodging intersecting with the collet side surface over a height greater than that of the hair-spring blade.

7. In the combination of claim 6, said lodging intersecting the collet side surface over a width smaller than the diameter of said lodging.

8. In the combination of claim 1, said blob extending outwardly beyond the hair-spring inner coil.

References Cited by the Examiner UNITED STATES PATENTS 995,537 6/1911 Hertner et a1 269-7 1,936,083 11/1933 Ridder 29460 2,606,482 8/1952 Sorensen et a1. 299-7 2,649,684 8/1953 Dolby 58-115 2,931,164 4/1960 Schweitzer et a1 58-115 3,116,547 1/ 1964 Nepple 2946O 3,139,364 6/1964 Fiechter 156-160 RICHARD B. WILKINSON, Primary Examiner. GERALD F. BAKER, Examiner. 

1. IN A HAIR-SPRING AND COLLET ASSEMBLY FOR TIME PIECES, IN COMBINATION, AN OUTER CONVEX SIDE SURFACE PORTION ON THE COLLET, A PORTION OF THE HAIR-SPRING INNER COIL HAVING AN INNER SIDE SURFACE APPLIED AGAINST SAID OUTER CONVEX SIDE SURFACE PORTION OF THE COLLET, A BOLB OF MATERIAL FIRMLY FIXED TO SAID PORTION OF THE HAIR-SPRING INNER COIL AND HAVING A PROJECTION EXTENDING INWARDS FROM THE INNER SIDE SURFACE THEREOF, AND A LODGING IN THE COLLET PROVIDED IN SAID OUTER CONVES SAID SURFACE PORTION THEREOF, THE INWARDLY EXTENDING PROJECTION OF SAID BLOB OF MATERIAL ENTERING SAID LODGING AND CONSTITUTING THEREWITH A FIXING CONNECTION ENSURING THE ANCHORAGE OF THE HAIR-SPRING TO THE COLLET. 